<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <link href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.0-alpha1/dist/css/bootstrap.min.css" rel="stylesheet"
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  <style>
    .item {
      display: inline-block;
      width: 100px;
      height: 100px;
      margin: 20px;
      border: 2px solid pink;
    }
  </style>
  <title>let练习</title>
</head>

<body>
  <div class="container">
    <h2 class="page-header">点击切换颜色</h2>
    <div class="item"></div>
    <div class="item"></div>
    <div class="item"></div>
  </div>
  <script src="./let练习.js"></script>
</body>

</html>